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Deformations of overloaded bands under pH-stable conditions in reversed phase chromatography
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry. (Fundamental Separation Science)
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry. (Fundamental Separation Science)
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry. (Fundamental Separation Science)
2011 (English)In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1218, no 15, 1966-1973 p.Article in journal (Refereed) Published
Abstract [en]

It has recently been demonstrated, using mathematical models, how peculiar overloaded band profiles of basic compounds are due to the local pH in the column when using low capacity buffers. In this study, overloaded peak shapes resulting after injection of carefully pH matched samples close to the pK(a) of the chosen solute are investigated primarily on two columns; one hybrid silica C18 column (Kromasil Eternity) and one purely polymeric column (PLRP-S), the latter lacking C18 ligands. It was found that distorted peaks of the basic test compound appear even though there is no difference in pH between the injected sample solution and the eluent; the previous explanation to why these effects occur is based on a pH mismatch. Thus, the unusual band shapes are not due to an initial pH difference. Furthermore, it was observed that the effect does not appear on polymeric columns without C18 ligands, but only on columns with C18 ligands, independently of the base matrix (silica, hybrid silica, polymeric).

Place, publisher, year, edition, pages
2011. Vol. 1218, no 15, 1966-1973 p.
National Category
Analytical Chemistry
Research subject
Analytical Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-151463DOI: 10.1016/j.chroma.2010.09.002ISI: 000289331200006PubMedID: 20888565OAI: oai:DiVA.org:uu-151463DiVA: diva2:410063
Available from: 2011-04-15 Created: 2011-04-12 Last updated: 2015-08-12Bibliographically approved
In thesis
1. Adsorption Studies with Liquid Chromatography: Experimental Preparations for Thorough Determination of Adsorption Data
Open this publication in new window or tab >>Adsorption Studies with Liquid Chromatography: Experimental Preparations for Thorough Determination of Adsorption Data
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Analytical chemistry is a field with a vast variety of applications. A robust companion in the field is liquid chromatography, the method used in this thesis, which is an established workhorse and a versatile tool in many different disciplines. It can be used for identification and quantification of interesting compounds generally present in low concentrations, called analytical scale chromatography. It can also be used for isolation and purification of high value compounds, called preparative chromatography. The latter is usually conducted in large scale with high concentrations. With high concentrations it is also possible to determine something called adsorption isotherms.

Determination of adsorption isotherms is a useful tool for quite a wide variety of reasons. It can be used for characterisation of chromatographic separation systems, and then gives information on the retention mechanism as well as provides the possibility to study column-column and batch-batch reproducibility. If a protein is immobilised on a solid support, adsorption isotherms can be used for pharmacological characterisation of drug-protein interactions. Moreover, they can be used for the study of unexpected chromatographic phenomena.

If the adsorption isotherm is known it is also possible to simulate chromatograms, and subsequently optimise the separation process numerically. The gain of a numerically optimised separation process is higher purity or yield of valuable compounds such as pharmaceuticals or antioxidants, as well as reducing the solvent usage. Taken all together, it saves time, money and the environment.

However, the process of the adsorption isotherm determination requires a number of careful experimental considerations and preparations, and these are the main focus of the thesis. Important steps along the way include the choice of separation system and of suitable analytes, preparation of mobile phases and sample solutions, calibration, determination of injection profiles and column void, and of course the adsorption isotherm determination method itself. It is also important to keep track of parameters such as temperature and pH. These issues are discussed in this thesis.

At the end, a description of useful methods for processing of the raw adsorption isotherm data is presented, as well as a brief passage on methods for numerical optimisation.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2014. 56 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1118
Keyword
Liquid chromatography, HPLC, UHPLC, Reversed phase, Preparative chromatography, Adsorption isotherm, Injection profile, Sample pH, pH stable conditions, Peak deformation, Band distortion, Overloaded band, Chiral preparative chromatography
National Category
Chemical Sciences Analytical Chemistry
Research subject
Analytical Chemistry
Identifiers
urn:nbn:se:uu:diva-216235 (URN)978-91-554-8858-1 (ISBN)
Public defence
2014-03-14, B22, BMC, Husargatan 3, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2014-02-14 Created: 2014-01-20 Last updated: 2014-04-29

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Edström, Lena

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